C2 Rear Cross Member Isolation Mount

[Alan Drake]

Have taken Diff out, now cleaning the gross member. Removed one Isolation Mount, but having trouble with second. Since these are both original (markings on rubber are PT- 770447). Soaked in penetrating oils, added a little heat, ect. Only moved it out 1/4". Don't want to push on smaller inside washer since it is only supported by rubber. Know it is recommended to use a pipe (3.75 size?) on outside edge of metal support around rubber, however that's a very small area. Anyone have a method?

After all this work I think the real question should be;
1 Are new isolation members recommended???
2 Who is a good source and are NOS worth the extra $ ?
3 Will judges want original ones?

Thanks
did do some searchs first, did a miss it

[Joe L.]

Re: C2 Rear Cross Member Isolation Mount

Alan------

Unless there is very obvious deterioration of the mounts (like, chunks out of them or severe cracking), there is absolutely no need to replace these mounts. They are "naturally" very well protected from the things that cause rubber to deteriorate.

[John H.]

Re: C2 Rear Cross Member Isolation Mount

Alan -

Yes, I'd replace them, considering the grief involved in having to do all that disassembly again when they fail. The good ones run about $75 each, and you'll never have to deal with them again. As with everything else, they need to APPEAR as if they could be original, not BE original.

[John H.]

Re: C2 Rear Cross Member Isolation - Addendum

One of my originals failed a year ago last summer, and really startled me when the upper flange sheared off the outer shell and allowed the crossmember to slide upward and ground out against the frame - very loud "bang", right behind the driver's seat. I replaced them both. Photo shows the failed mount before I replaced them.

[Wayne M.]

Doubt 1st design cushions still out there

Your '64 (and all '63s and '65's up to S116516 had the 4-tab design, subject to pull-out. See the 2 pages (links below) for details of the Tech Service Bulletin, scanned from Vette Vues. Pic immediately below is of 2nd design after mid-'65 (note part # as mentioned in TSB); view of side facing the road.

Don't know why you'd want to replace them if they were good to begin with. Can't find specific reference in the '65 TM & JG to the crossmember or the ruber mounts, but am sure that you'd get nailed more for 8-tab design (replacement) than cracked rubber, especially at the regional judging level.

TSB page 1:
TSB page 2:
Note to John H. I've never heard of a mount failing in the direction that your picture shows. The TSB was to prevent the cross-member pulling DOWN (bending the tabs in the process).

[Alan Drake]

Re: Back to Old Ones - Thanks *NM*

[John H.]

Re: Doubt 1st design cushions still out there

Wayne -

I'm intrigued by the failure of the "tabs", "under certain driving conditions" stated in the TSB; there is ZERO force against the tabs unless the car is "catching air" or sitting on a frame contact hoist.

Mine failed due to corrosion of the upper flange on the outer sleeve of the bushing - most of the flange simply sheared right off, and the bushing on the other side wasn't far from doing the same thing.

[John H.]

Re: Doubt 1st design cushions still out there

Wayne -

I'm intrigued by the failure of the "tabs", "under certain driving conditions" stated in the TSB; there is ZERO force against the tabs unless the car is "catching air" or sitting on a frame contact hoist.

Mine failed due to corrosion of the upper flange on the outer sleeve of the bushing - most of the flange simply sheared right off, and the bushing on the other side wasn't far from doing the same thing.